1. Field of the Invention
This patent is directed to the field of detection of trace impurities in gases and particularly to a portable analyzer and process for the detection of carbonyl sulfide present in low part-per-million and part-per-billion concentrations in gases such as carbon dioxide gas.
2. Description of the Prior Art
Carbon dioxide gas is extensively used in the soft drink as well as the beer industries. Even very small amounts of carbonyl sulfide while odorless itself produces off-flavors in the food products in which the carbon dioxide contaminated with carbonyl sulfide is used. It is very difficult to detect low part-per-million (PPM) and part-per-billion (PPB) concentrations of carbonyl sulfide (COS) in gases such as carbon dioxide (CO.sub.2).
It is desirable in the beverage industry to have an extremely accurate carbonyl sulfide analyzer which is inexpensive, portable, and extremely accurate to the extent of detecting carbonyl sulfide in carbon dioxide of less than 1 PPM.
One method for detecting carbonyl sulfide in gases is by means of a color tube produced by Bendix. This tube is based on an acid-base system which converts the carbonyl sulfide to sulfuric acid. The presence of carbonyl sulfide is indicated by a color change. The sensitivity of this test is not very good since the smallest amount of carbonyl sulfide which can be detected is 10 PPM. Moreover, it is not suitable for the detection of carbonyl sulfide in carbon dioxide because the carbon dioxide also reacts in the color tube.
Another means for detection of carbonyl sulfide is the use of a flame photometric detector (FPD). This device attaches to a gas chromatograph and is very accurate. The main drawbacks are that it is extremely costly, large in size, and requires a source of hydrogen and air as a fuel and nitrogen as a carrier gas.